new source of RFI (Radio Frequency Interference) LED signs

 Here is a short video showing some RFI coming from a LED sign from local club member, when start to look around you find many of these signs at schools, churches and shops.

This example is listening on a 2metre band FM radio.   It be nice to find the manufacturer to let them know these signs are radiating RFI.

IMG_2254.MOV - Google Drive

RFI from Foxtel IQ2 STB's on 10m & 6m bands

I noticed hearing modulated signals across 29 MHz band and 52-53 MHz bands when scanning the FM segments from time to time, not clean carriers but data  modulated carriers appearing then disappearing.  By accident, I just happening to hear this occurring one day and by chance doors were open in the house where I could see through doorways to the TV set where the XYL was flicking through Foxtel channels.  OMG, the modulation on the signal varying as channels are being changed, here was the culprit, our Foxtel IQ2 STB (set-top-box).

I got out the Uniden handheld scanner and did some sniffing around the  STB, but no, it seems to be radiating from the LED flat panel TV,  turned power off to the TV but noise still radiating, unplug power cable from TV and noise still there, unplug HDMI cable to Foxtel STB, then RFI signal drops off drastically.

Sniff closer to Foxtel box, very strong signal from the ethernet RJ45 cable and the HDMI cable.  Remove both cables and noise almost non-existant.  sniff the power cord at the rear of Foxtel STB and noise still very low,  plugin the HDMI and ethernet cables one at a time, pretty equally as strong.
I noticed it detected noise on 2m band too, but much lower levels than that of 10m and 6m bands.

Outcome, the Foxtel box itself not radiating but very bad when HDMI cable plugged into a LED flat panel TV, as it using the TV as a RFI antenna.  As a secondary source of RFI it using the Ethernet RJ45 cable as a nice antenna too. I think from memory the IQ2 box made by Pace.

Solution, grabbed my box of various  sized ferrite clipon cores, added 7mm ID and 9mm ID cores on the power, RJ-45 and HDMI cables, closest to the rear of the Foxtel IQ2 box, this suppressed the RFI  sufficiently, in terms of 10m and 6m bands, could now only receive RFI up to about 1 metre from the STB, whereas my  transceiver antenna could hear it from 20 metres away.   I also tried clamping some ferrite cores over the two coax leads running to the satellite dish LNA but that made absolutely no difference, so RFI not radiating back out via coaxes, that I could see.

Modifications for the TYT TH-9800 FM quad-bander mobile transceiver

These TH-9800  quad band FM transceivers  (a clone of the Yaesu FT-8900 transceiver) have an issue of blowing the transmit driver FET.  I have documented a modification to fix this, as it would be a considerable amount of work to replace the drive FET, or even the PA FET for that matter. Easier to do the mod and run at less output power, better than having a dead tx PA. It basically adding a 8v (7808) regulator into the supply circuit for the Driver FET,  which is fed hot from the 13.8v DC input.

http://www.qsl.net/vk2kfj/th9800.html

SDR update

if you had played with,  or attempted to play with those little USB TV dongles,  e.g. the black dongle that Andrew VK3BQ sent as link for on ebay end of last year.  The black rtl2838 based dongle is more sensitive and less prone to image signals than the white rtl2832 based dongle we had used in the past.

I can advise that the  SDR#  (sdrSharp) website have greatly  improved their download and install package and install procedures, it's now a much easier task. And the rtlsdr.org site have also improved their install procedures instructions, for those using RTL based dongles.

The latest Zadig USB driver installer is much improved too. Note: two versions of Zadig, one for XP and another version  for Vista,Win7 & Win8.

begin here at the SDR# downloads area:

http://sdrsharp.com/index.php/downloads

which includes links to install procedures on rtlsdr.org for MS Windows and Linux

i.e.

http://rtlsdr.org/softwarewindows

Somehow I broke my SDR# installation on my notebook last year whilst trying to update it and could not get it running properly, but I did the download and reinstall yesterday and now it all works great, I can even swap between dongles to compare them, both dongles work fine. Really pleased with it now.